1. Field of the Invention
The invention relates to a heat treatment device, and particularly to a heat treatment device performing heat treatment on a work substrate (i.e., a substrate to be treated) such as a semiconductor wafer or an LCD substrate.
2. Description of the Background Art
In a conventional photoresist step, which is one of semiconductor manufacturing steps, resist is applied over a surface of a semiconductor wafer or a substrate of an LCD substrate or the like (which will be referred to as a “wafer” hereinafter), and is exposed with a predetermined pattern. Then, a developer liquid is supplied onto the surface of the wafer, and development is performed to form a resist pattern. For protecting the resist, a step of applying a protective film over the surface of a resist layer is generally incorporated into the above photoresist step.
In recent years, it has been increasingly requested to increase an exposure resolution according to miniaturization of device patterns and reduction in thickness thereof. For increasing the exposure resolution, a method in which an anti-reflective coating (s) are arranged under and/or above a resist has been employed. A technology has also been known as another method for the miniaturization. In this technology, a photoresist pattern is formed by performing exposure multiple times on a photoresist on a substrate with a predetermined mask patterns, and then the photoresist pattern is miniaturized using plasma ashing or the like.
In the above miniaturizing technology, a multi-layer film is formed over the surface of the wafer, and further the multiple applying operations and the subsequent heat treatment are repeated. Therefore, the wafer may warp due to stacking of different kinds of films and changes in temperature and the like. For example, when a chemically amplified resist is used and the wafer warps during cooling performed after the heat treatment subsequent to the exposure, variations occur in state of temperature lowering to a temperature (e.g., 50 degrees C.) at which an acid catalytic reaction on the wafer surface stops, and a line width cannot be kept uniform.
A device for suppressing a warp of a wafer has been known (e.g., Japanese Patent Laying-Open No. 2006-210400). This device has a measuring unit for measuring a warp, a plurality of blow/suction holes selectively blowing and drawing a gas, and a control unit performing the blowing or drawing by each blow/suction holes according to a measurement result provided by the warp measuring unit.
In another known device (e.g., Japanese Patent Laying-Open No. 11-214486), a plurality of projections are arranged on a top surface of a stage carrying a wafer, or a seal ring is arranged for contact with a peripheral portion of the wafer in addition to arrangement of the plurality of projections, and an air is drawn out from a space between the wafer and the stage to keep a uniform space between the wafer and the stage.
However, the technology disclosed in Japanese Patent Laying-Open No. 2006-210400 is configured to control the blowing or drawing by the blow/suction holes according to the measurement result of the warp measuring unit that measures the warp. Therefore, the structure is complicated, and further a time for suppressing the warp is required so that it is difficult to perform the cooling processing within a short time after the heat treatment.
According to the technology disclosed in Japanese Patent Laying-Open No. 11-214486, the structure can be simpler than that in Japanese Patent Laying-Open No. 2006-210400, but is configured to press the wafer onto the projections by keeping a negative pressure in a space between the stage and the wafer laid on the plurality of projections arranged on the top surface of the stage. Therefore, a negative pressure must be kept in whole the space between the wafer and the stage, and a large negative pressure is required for such a state. Also, when the wafer warps into a complicated form, it is difficult to press reliably the wafer onto the projections, and it may be impossible to suppress reliably the warp of the wafer.